it s usually transport indeed lead casing. mexican authorities say if it s removed from that. translator: the raid ag, gamma-rays in this case, is harmful and dangerous to your health. reporter: security officials have long been concerned that cobalt-60 cooling used by terrorists in a so-called dirty bomb like those seen in this simulation. i asked a homeland security expert if ache truck ball exploded at a crowded city corner damage the buildings, you ll have injuries and fatalities from the explosion. but the dirty ball, and it s a dirty ball, because it has about this much cobalt-60, it s going to contaminate the area. it s not an immediate threat to public health, but you could not live or work here for the next year or so if it were not cleaned up. it could increase your probability of cancer. reporter: experts say it wouldn t be difficult to put cobalt-60 in a conventional ball. so when the device explodes, the